For the purpose of this study, 14 lean women (BMI ≤ 25 kg/m2) and 36 obese women (BMI 30-39 kg/m2) with PCOS as well as 14 lean and 14 obese control women will be recruited to determine their insulin sensibility (insulin levels, M-value, metabolic clearance rate of glucose)and FFA metabolism (FFA levels, rythm of apparition and disapearance of FFA) during a 75g oral glucose tolerance test and a 2-step insulin-glucose clamp.